Add dialect options

Author: yoavcloud

src/dialect/mod.rs

@@ -1060,6 +1060,22 @@ pub trait Dialect: Debug + Any {
     fn supports_space_separated_column_options(&self) -> bool {
         false
     }
+
+    /// Returns true if the dialect supports `ALTER TABLE tbl ALTER COLUMN col TYPE <type>`
+    /// without specifying `SET DATA` before `TYPE`.
+    ///
+    /// - [Redshift](https://docs.aws.amazon.com/redshift/latest/dg/r_ALTER_TABLE.html#r_ALTER_TABLE-synopsis)
+    /// - [PostgreSQL](https://www.postgresql.org/docs/current/sql-altertable.html)
+    fn supports_alter_column_type_without_set(&self) -> bool {
+        false
+    }
+
+    /// Returns true if the dialect supports `ALTER TABLE tbl ALTER COLUMN col SET DATA TYPE <type> USING <exp>`
+    ///
+    /// - [PostgreSQL](https://www.postgresql.org/docs/current/sql-altertable.html)
+    fn supports_alter_column_type_using(&self) -> bool {
+        false
+    }
 }
 
 /// This represents the operators for which precedence must be defined

src/dialect/postgresql.rs

@@ -258,4 +258,12 @@ impl Dialect for PostgreSqlDialect {
     fn supports_set_names(&self) -> bool {
         true
     }
+
+    fn supports_alter_column_type_without_set(&self) -> bool {
+        true
+    }
+
+    fn supports_alter_column_type_using(&self) -> bool {
+        true
+    }
 }

src/dialect/redshift.rs

@@ -129,4 +129,8 @@ impl Dialect for RedshiftSqlDialect {
     fn supports_string_literal_backslash_escape(&self) -> bool {
         true
     }
+
+    fn supports_alter_column_type_without_set(&self) -> bool {
+        true
+    }
 }

src/parser/mod.rs

@@ -8736,7 +8736,9 @@ impl<'a> Parser<'a> {
                 AlterColumnOperation::DropDefault {}
             } else if self.parse_keywords(&[Keyword::SET, Keyword::DATA, Keyword::TYPE]) {
                 self.parse_set_data_type(true)?
-            } else if self.parse_keyword(Keyword::TYPE) {
+            } else if self.dialect.supports_alter_column_type_without_set()
+                && self.parse_keyword(Keyword::TYPE)
+            {
                 self.parse_set_data_type(false)?
             } else if self.parse_keywords(&[Keyword::ADD, Keyword::GENERATED]) {
                 let generated_as = if self.parse_keyword(Keyword::ALWAYS) {
@@ -8905,7 +8907,9 @@ impl<'a> Parser<'a> {
 
     fn parse_set_data_type(&mut self, had_set: bool) -> Result<AlterColumnOperation, ParserError> {
         let data_type = self.parse_data_type()?;
-        let using = if self.parse_keyword(Keyword::USING) {
+        let using = if self.dialect.supports_alter_column_type_using()
+            && self.parse_keyword(Keyword::USING)
+        {
             Some(self.parse_expr()?)
         } else {
             None

tests/sqlparser_common.rs

@@ -5046,6 +5046,7 @@ fn parse_alter_table_alter_column() {
 
 #[test]
 fn parse_alter_table_alter_column_type() {
+    let alter_stmt = "ALTER TABLE tab";
     match alter_table_op(verified_stmt(
         "ALTER TABLE tab ALTER COLUMN is_active SET DATA TYPE TEXT",
     )) {
@@ -5062,6 +5063,23 @@ fn parse_alter_table_alter_column_type() {
         }
         _ => unreachable!(),
     }
+
+    let dialects = all_dialects_except(|d| d.supports_alter_column_type_without_set());
+    let res =
+        dialects.parse_sql_statements(&format!("{alter_stmt} ALTER COLUMN is_active TYPE TEXT"));
+    assert_eq!(
+        ParserError::ParserError("Expected: SET/DROP NOT NULL, SET DEFAULT, or SET DATA TYPE after ALTER COLUMN, found: TYPE".to_string()),
+        res.unwrap_err()
+    );
+
+    let dialects = all_dialects_except(|d| d.supports_alter_column_type_using());
+    let res = dialects.parse_sql_statements(&format!(
+        "{alter_stmt} ALTER COLUMN is_active SET DATA TYPE TEXT USING 'text'"
+    ));
+    assert_eq!(
+        ParserError::ParserError("Expected: end of statement, found: USING".to_string()),
+        res.unwrap_err()
+    );
 }
 
 #[test]